An ink jet printer body includes an ink jet head, which ejects ink toward paper. One type of ink jet recording apparatus includes a plurality of head bodies arranged in a paper width direction or a paper length direction. In such an apparatus, a position of an ejection port at an end portion where a head body is adjacent to another head body is adjusted. The plurality of head bodies are positioned with respect to a printer body to cause each row of ejection ports to be parallel to a main scanning direction, thereby obtaining an image recording region. An ink jet structure member supporting the head bodies is attached to an attachment plate on the printer body side via a reference plate, and the plurality of head bodies are disposed to be parallel to each other with respect to a position of the reference plate. Nevertheless, if a coefficient of thermal expansion of the reference plate is not considered, with respect to driving the head bodies for ejection, the head bodies and the ink jet structure member thermally expand due to heat generated by a driver integrated circuit (IC). An ink jet printer should prevent deterioration in quality of printing due to an occurrence of relative misalignment or an occurrence of thermal distortion between the heads adjacent to each other caused by thermal expansion thereof when a plurality of the heads are arranged in a longitudinal direction.
When the coefficient of thermal expansion of the reference plate is greater than a coefficient of thermal expansion of the attachment plate, an elongated portion of the reference plate in the longitudinal direction becomes greater than an elongated portion of the attachment plate.